In the prior art it has been common for belt sanders to require manual adjustment of pulley alignment for belt tracking. Such manual adjustment is often difficult, inconvenient and time-consuming. Alignment adjustment is usually required after belt replacement. Alignment readjustment may be required during sander operation. In belt sanders having no provision for manual adjustment of pulley alignment, it has been common to equip belt pulleys with edgewise flanges to assist in belt tracking but friction between pulley flanges and belt often causes rapid belt wear. In addition, the prior art devices are of rather complicated construction resulting in increased expense, both in material cost and assembly and in increased opportunity for malfunction.